It is well known in the prior art that vulcanized rubber has a high coefficient of friction. The present invention utilizes lubricants and high temperature dispergents to improve the distribution of the crumb rubber to the polymer matrix, usually at 200° F. to 550° F. along with improving the fluidity and processibilty of the overall compound. The dispergents cover the surface of the crumb rubber, due to their low viscosity and the processing temperature; they enable easy separation of the particles of crumb rubber and aid in the mixing with plastic material. Common dispergents/lubricants/process/aides/antifoaming agents useful to the present invention include but are not limited to polar lubricants or process aides, such as tall oil, antifoaming agents such as silicone, and dispergents such as calcium stearate.
Tall oils include fatty acids and rosin acids in total over 80% by weight, with the rest being tall oil pitches. Fatty acids have long aliphatic chains and very polar carboxyl groups. These carboxyl group can make strong interactions with the polar spots on the surface of the crumb rubber. The polar spots are the filler particles such as carbon black, silica or other fillers that are used in the tire production. The long aliphatic chain has a similar structure to polyethylene and polypropylene and can interact with those matrixes extremely well. Tall oil helps improve dispersion of the crumb rubber. Also, due to the amphiphilic structure (contains polar and non-polar sides) tall oil improves interconnection between the crumb rubber and plastic matrix. Tall oil can be considered to be a coupling agent. Thus, lubricants such as tall oil are coupling agents used in order to improve the bonds between filler (rubber) and polymer matrix (plastic).
The present invention goes well beyond the prior art in expanding lubricants such as tall oil, fatty acids, and by-products of tall oil production. The present invention's viscoelastic modifying affects function with both amorphous and crystalline thermoplastic groups. Of special use in the present invention is the thermoplastic group known as polyolefins.
The present invention provides for the use of crumb rubber in combination with lubricants (polar and nonpolar), polyolefins and other organic compounds and with a coupling agent, such as maleinated polyethylene. Metallocene is also almost always used with this combination.